The present invention generally relates to communicating via telemetry with implantable medical devices and instruments. Specifically, the invention relates to a method and an apparatus for enabling the sensing of outputs, and/or real time communication with, various medical devices for chronic patient management.
In recent years, implantable electronic device technology has rapidly advanced. Sizes and weights of implantable devices have decreased; while functionality has increased. These advances have created a corresponding demand for two-way communication or telemetry between the implantable electronic device and an external device, (e.g. a programmer). In a pacemaker system, a programmer downloads to an implanted pacemaker, data such as operating parameters. Likewise, data may flow in the opposite direction; that is, from the implantable device to the programmer for analysis. In fact, modem pacemakers are capable of storing significant amounts of data about the patient (e.g., average heart rate) and the pacemaker itself (e.g. battery voltage), which may need to be frequently transmitted to the programmer for, evaluation by the physician.
A programmer used during a telemetry procedure is typically positioned remotely from the patient""s implanted device. A programming head of the programmer unit, e.g., a wand or some other extendible head, containing at least an antenna, is connected to the remainder of the programmer unit via a stretchable coil cable and is positioned over the patient""s implanted device site for programming or telemetry interrogation of the implanted device. The programmer typically consists of one or more microprocessors and contains programmable memory capable of storing executable programs under the control of the operator via a user interface. The implantable medical device may receive command instructions from the programmer. Such command instructions are referred to herein as xe2x80x9cdownlink transmissionsxe2x80x9d, i.e., transmissions from the external device to the implanted medical device. In one example, the received command instructions may include program instructions or steps for directing the operation of the implantable medical device or may also include data such as program limits and timing data.
Similarly, the implanted medical device may transmit data to the external device (e.g., programmer unit) and the transmissions are referred to herein as xe2x80x9cuplinkxe2x80x9d transmissions. The programmer may function to receive data from the implanted medical device as well as to transmit the commands to the implanted device. Communication between the implanted device and the external device may be limited to one-way transmissions or alternatively may include two-way transmissions. The communication between the implanted medical device and the external device is facilitated by corresponding receiving and transmitting circuitry included within the implanted medical device and the external device. Both the implanted medical device and the external device include antenna structures coupled to the receiver and transmitter-circuitry for transmitting and receiving electromagnetic energy.
Conventional telemetry systems typically enclose the antenna or antennas of the implanted medical device inside the housing or case of the implanted device. Such housings are typically metallic in nature and may be made of titanium or titanium alloys. The metal housings may act as low pass filters to limit the bandwidth of signals transmitted from and received by the implanted medical devices. In addition, telemetry systems that have antennas enclosed in the housing generally have undesirably low transmission rates.
With respect to conducting actual telemetric communications with implanted devices, it is preferable to use the near H field from the coil antenna rather than the E field. This is because the H field wave impedance is much less than the E field wave impedance, thereby allowing lower loss signal transmission through the metal housing and through the patient""s skin (the near field is generally considered to be less than ⅙th of the wave length of the carrier wave). Therefore, uplink telemetry range depends upon the near field magnetic field strength or amplitude. The magnetic field strength, in turn, depends on the number of coil turns in the antenna, the area of the coil, and the coil current. The uplink transmitter efficiency depends on the coil quality factorxe2x80x9cQxe2x80x9d. To increase the telemetry uplink range, the magnetic field intensity must be maintained at an increased distance from the implanted device. The magnetic field may be increased by: adding more turns to the coil; making the coil antenna larger in area, winding it with a larger radius or by driving the coil with a larger coil current. The larger the coil Q, the more efficient the uplink transmitter circuit becomes. It should be noted that, for either uplink or downlink, it would be desirable to utilize only near-field magnetic fields (H fields), which do not require federal licensing since their amplitude falls off rapidly with link range.
Existing telemetry or equivalent systems rely on programming heads that must be precisely placed and positioned on the patient""s IMDs (implanted medical devices) in order to transmit data. This is because the antenna is disposed in the moveable programmer head and the antenna must be placed in close proximity to the implantation site to effect agreeable data transmission link. The inability of the physician to see the IMD makes it even more difficult to establish the data link while the reliability of the data link is highly dependent on the signal strength that is obtained by proper: programming head orientation. A further complicating factor involves the physician handling the programming head while performing other important tasks. Constant repositioning of the programming head in order to maximize received signal strength makes completing the, telemetry functions undesirably difficult. Finally, establishing the telemetry in the exact location for a patient or a healthcare practitioner may be difficult if they have limited dexterity or if they need to hold the programming head in one position for extended periods of time.
Various embodiments of the present invention are directed to addressing the above and other needs in connection with providing a reliable, economical and non-invasive system for conveniently and chronically collecting cardiac and other IMD (implantable medical device) data. According to one aspect of the invention, collecting IMD data is simplified in order to promptly initiate, modify or control therapy and diagnosis in connection with chronic patient monitoring. In an example embodiment, a component of a telemetry or equivalent communications system includes a wearable article such as a vest, a wrist attachment or similar apparel or accessory that facilitates communication with an IMD to exchange clinical information from the IMD in the patient.
According to one embodiment of the invention, a telemetry arrangement for communicatively coupling an implanted medical device with a medical communications system has been discovered. The telemetry arrangement includes an article configured and arranged to be physically coupled to and donned on a body. The arrangement further includes an antenna member located on the article and configured and arranged to establish a communications link between the implanted device and the medical communications system.
According to another embodiment of the invention, a method and a system of establishing a telemetric communications link between an implantable device and a medical information communications system includes donning an article having an antenna member located thereon. A data communications link is then established between the implantable device and the medical communications system wherein a portion of the communications link is physically coupled to a body.
The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures in the detailed description that follow more particularly exemplify these embodiments.